Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A polycrystalline diamond cutting (PDC) element of a drill bit of a
downhole drilling tool is provided. The PDC element having a substrate, a
diamond table and at least one pattern. The diamond table has an initial
cutting edge along a periphery thereof. The pattern integrally formed
within the diamond table. The pattern(s) defining at least one
discontinuity about the diamond table that, in operation, selectively
breaks away upon impact to create new cutting edges in the diamond table
whereby a sharp cutting edge is continuously exposed to a material being
cut.

Claims:

1. A polycrystalline diamond cutting element of a drill bit of a downhole
drilling tool, comprising: a substrate; a diamond table positionable on
the substrate, the diamond table having an initial cutting edge along a
periphery thereof; and at least one pattern integrally formed within the
diamond table, the at least one pattern defining at least one
discontinuity about the diamond table that, in operation, selectively
breaks away upon impact to create new cutting edges in the diamond table
whereby a sharp cutting edge is continuously exposed to a material being
cut.

2. The polycrystalline diamond cutting element of claim 1, wherein the
discontinuity is formed along the initial cutting edge within the diamond
table react to operating loads to direct shearing forces into the diamond
table to fracture the initial cutting edge and to form the new cutting
edges.

3. The polycrystalline diamond cutting element of claim 1, wherein the at
least one pattern comprises a mesh pattern.

4. The polycrystalline diamond cutting element of claim 1, wherein the at
least one pattern comprises a honeycomb pattern.

5. The polycrystalline diamond cutting element of claim 1, wherein the at
least one pattern is sintered together with the diamond table and the
substrate under conditions of ultra high temperatures and pressures.

8. The polycrystalline diamond cutting element of claim 1, wherein the at
least one discontinuity defines a fracture surface along the initial
cutting edge.

9. The polycrystalline diamond cutting element of claim 1 wherein the at
least one discontinuity resides close to the initial cutting edge and
follows an edge geometry of the diamond table.

10. The polycrystalline diamond cutting element of claim 1, wherein the
diamond table wears over time such that the at least one pattern is
exposed upon wear and/or impact damage to the initial cutting edge of the
diamond table.

11. The polycrystalline diamond cutting element of claim 1, wherein the
diamond table wears quickly such that the at least one pattern wears away
quickly to expose a controlled geometry of the new cutting edges, thereby
reducing loss of the diamond table on subsequent impacts.

12. The polycrystalline diamond cutting element of claim 1, wherein the
at least one pattern has one of a snowflake configuration, a ring
configuration, a plate configuration, a perforated configuration and
combinations thereof.

13. The polycrystalline diamond cutting element of claim 1, wherein the
at least one pattern comprises a plurality of patterns, each of the
plurality of patterns defining an additional discontinuity parallel to a
top surface of the diamond table.

14. The polycrystalline diamond cutting element of claim 1, wherein the
at least one pattern has an angled periphery positionable about the
cutting edge.

17. A polycrystalline diamond cutting element of a drill bit of a
downhole drilling tool, comprising: a substrate; a diamond table
positionable on the substrate, the diamond table having an initial
cutting edge along a periphery thereof; and at least one pattern within
the diamond table, the at least one pattern comprising at least one
discontinuity defining a plane of weakness within the diamond table that,
in operation, selectively breaks away along the plane of weakness to
continuously expose fracture surfaces in the diamond table whereby a
sharp cutting edge is continuously exposed to a material being cut.

18. The polycrystalline diamond cutting element of claim 17, wherein the
at least one discontinuity along the initial cutting edge creates a
fracture surface which allows exposure of a new cutting edge to the
material being cut.

19. The polycrystalline diamond cutting element of claim 17, wherein the
at least one pattern has a periphery defining an angle of a chamfer that
creates a fault line in the diamond table which is controlled by an angle
of a mesh of the at least one pattern.

20. A method of drilling with a downhole drilling tool having a drill
bit, comprising: positioning a plurality of polycrystalline diamond
cutting elements on the drill bit, each of the plurality of
polycrystalline diamond cutting elements comprising: a substrate; a
diamond table positionable on the substrate, the diamond table having an
initial cutting edge along a periphery thereof; and at least one pattern
integrally formed within the diamond table, the at least one pattern
defining at least one discontinuity about the diamond table that;
continuously exposing a sharp cutting edge by selectively breaking away
portions of the diamond table upon impact to create a new cutting edge in
the diamond table as the drill bit is advanced into the earth.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent
Application Ser. No. 61/367,026 filed on Jul. 23, 2010, the entire
contents of which is hereby incorporated by reference.

[0005] Polycrystalline diamond and polycrystalline diamond-like elements
are known, for the purposes of this specification, as PDC elements. PDC
elements are typically formed from carbon based materials. Another
somewhat similar diamond-like material is known as carbonitride (CN) as
described in U.S. Pat. No. 5,776,615.

[0006] PDC elements are typically formed from a mix of materials processed
under high-temperature and high-pressure into a polycrystalline matrix of
bonded diamond crystals. PDC elements may be manufactured in a process
which uses catalyzing materials during their formation. These catalyzing
materials may form a residue which may impose a limit upon the maximum
useful operating temperature of a PDC element while in service.

[0007] One manufactured form of a PDC element may be a two-layer or
multi-layer PDC element where a facing table of polycrystalline diamond
material is integrally bonded to a substrate of less hard material, such
as cemented tungsten carbide. The PDC element may be in the form of a
circular or part-circular tablet, or it may be formed into other shapes
suitable for drilling applications or for other applications, such as
friction bearings, valve surfaces, indenters, tool mandrels, etc. PDC
elements of this type may be used for a wide range of applications where
a hard wear and erosion resistant material may be required. PDC elements
may also find particular usage in earth boring drill bits, where the
substrate of the PDC element may or may not be brazed to a carrier, and
this carrier may also typically be cemented tungsten carbide. This
configuration for PDC elements may be used in fixed cutter or rolling
cutter earth boring bits. These PDC elements may be received in a socket
of the drill bit, brazed on a face of the drill bit, or infiltrated in a
body of a `matrix` type drill bit. PDC elements may also be fixed to a
post in a machine tool for use in machining various non-ferrous
materials.

[0008] PDC elements may be formed by sintering diamond powder with a
suitable binder-catalyzing material in a high-pressure, high-temperature
press. Techniques for forming PDC elements are described, for example, in
U.S. Pat. No. 3,141,746. In one process for manufacturing PDC elements,
diamond powder is applied to the surface of a preformed tungsten carbide
substrate incorporating cobalt. The assembly is then subjected to very
high temperature and very high pressure in a press. During this process,
cobalt migrates from the substrate into the diamond layer (or table) and
acts as a binder-catalyzing material, causing the diamond particles to
bond to one another with diamond-to-diamond bonding, and also causing the
diamond layer to bond to the substrate.

[0009] The completed PDC element may have at least one body with a matrix
of diamond crystals bonded to each other with many interstices containing
a binder-catalyzing material as described above. The diamond crystals may
have a first continuous matrix of diamond, with the interstices forming a
second continuous matrix of interstices containing the binder-catalyzing
material. In addition, there may be a relatively few areas where the
diamond-to-diamond growth has encapsulated some of the binder-catalyzing
material. These `islands` may not be part of the continuous interstitial
matrix of binder-catalyzing material.

[0010] In one form, the diamond body may have from about 85% to about 95%
of diamond by volume and the binder-catalyzing material may have the
other about 5% to about 15% diamond. Such a PDC element may be subject to
thermal degradation due to differential thermal expansion between the
interstitial cobalt binder-catalyzing material and diamond matrix
beginning at temperatures of about 400 degrees C. Upon sufficient
expansion, the diamond-to-diamond bonding may be ruptured and cracks and
chips may occur.

[0011] When used in highly abrasive cutting applications, such as in drill
bits, these PDC elements may typically wear or fracture, and there has
been a relationship observed between wear resistance of the PDC elements
and their impact strength. This relationship may be attributed to the
catalyzing material remaining in the interstitial regions among the
bonded diamond crystals which contributes to the thermal degradation of
the diamond layer.

[0012] A portion of this catalyzing material may be preferentially removed
from a portion of the working surface in order to form a surface with
much higher abrasion resistance without substantially reducing its impact
strength. Examples of such PDC elements designed for increased strength
characteristic are described in U.S. Pat. Nos. 6,601,662; 6,592,985 and
6,544,308.

[0013] Certain types of PDC elements (e.g., diamond structures) may form
protruding lips as the cutter drills. These lips may repeatedly form and
then break off as the cutter drills into the earth, so as to always
present a sharp cutting edge to the formation. However, a certain amount
of wear may occur in the cutting element to form the lips.

[0014] Various types of PDC elements have become widely used in the
oilfield drilling industry over time, and attempts have been made to
increase the cutting efficiency of these PDC elements. However, the
drilling market has remained competitive and calls for ever higher
drilling rates of penetration. The techniques provided herein are
designed to provide these and other capabilities.

SUMMARY OF THE INVENTION

[0015] Disclosed herein is a polycrystalline diamond cutting element for a
borehole drilling downhole drill bit tool that has a substrate with a
diamond table. The diamond table has an initial cutting edge along a
periphery thereof; and at least one pattern integrally formed within the
diamond table. The pattern defines at least one discontinuity about the
diamond table that, in operation, selectively breaks away upon impact to
create new cutting edges in the diamond table whereby a sharp cutting
edge is continuously exposed to a material being cut.

[0016] The polycrystalline diamond cutting element may have a
discontinuity that is formed along the initial cutting edge within the
diamond table that reacts to operating loads to direct shearing forces
into the diamond table to fracture the initial cutting edge and to form
the new cutting edges. Furthermore, the polycrystalline diamond cutting
element may have at least one pattern that is a mesh pattern.

[0017] The above polycrystalline diamond cutting element may also have a
honeycomb pattern, where the pattern is sintered together with the
diamond table and the substrate under conditions of ultra high
temperatures and pressures, this may also include a polycrystalline
diamond grit, and the substrate may have a tungsten carbide substrate.
Furthermore, the polycrystalline diamond cutting element may have at
least one discontinuity that is a fracture surface along the initial
cutting edge. The discontinuity may reside close to the initial cutting
edge and follow an edge geometry of the diamond table.

[0018] In addition, the diamond table of the above polycrystalline diamond
cutting element may wear over time such that the at least one pattern is
exposed upon wear and/or impact damage to the initial cutting edge of the
diamond table.

[0019] The above polycrystalline diamond cutting element may also have a
diamond table that wears quickly, such that the at least one pattern
wears away quickly to expose a controlled geometry of the new cutting
edges, thereby reducing loss of the diamond table on subsequent impacts.

[0020] The polycrystalline diamond cutting element may also have at least
one pattern that is one of a snowflake configuration, a ring
configuration, a plate configuration, a perforated configuration and
combinations thereof, and the pattern may be a plurality of patterns,
each having an additional discontinuity parallel to a top surface of the
diamond table. One of the patterns may have an angled periphery
positionable about the cutting edge. The pattern may be made of tungsten
carbide, and/or scattered pellets of aggregated carbon nano-rods.

[0021] In addition a polycrystalline diamond cutting element for a drill
bit of a downhole drilling tool is described that is made up of a
substrate, a diamond table positionable on the substrate. The diamond
table may have an initial cutting edge along a periphery thereof; and at
least one pattern within the diamond table. The at least one pattern may
comprise a discontinuity defining a plane of weakness within the diamond
table that, in operation, selectively breaks away along the plane of
weakness to continuously expose fracture surfaces in the diamond table
whereby a sharp cutting edge is continuously exposed to a material being
cut.

[0022] This polycrystalline diamond cutting element may have at least one
discontinuity along the initial cutting edge which creates a fracture
surface allowing exposure of a new cutting edge to the material being
cut. In addition, the at least one pattern may have a periphery defining
an angle of a chamfer that creates a fault line in the diamond table
which is controlled by an angle of a mesh of the at least one pattern.

[0023] Also disclosed is a method of drilling downhole with a drill bit by
positioning a plurality of polycrystalline diamond cutting elements on
the drill bit, each of the plurality of polycrystalline diamond cutting
elements having a substrate, a diamond table positionable on the
substrate, the diamond table having an initial cutting edge along a
periphery thereof; and at least one pattern integrally formed within the
diamond table. The pattern may define at least one discontinuity on the
diamond table that may continuously expose a sharp cutting edge by
selectively breaking away portions of the diamond table upon impact to
create a new cutting edge in the diamond table as the drill bit is
advanced into the earth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] So that the above recited features and advantages of the present
invention can be understood in detail, a more particular description of
the invention, briefly summarized above, may be had by reference to the
embodiments thereof that are illustrated in the appended drawings. It is
to be noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are, therefore, not to be considered
limiting of its scope. The figures are not necessarily to scale, and
certain features and certain views of the figures may be shown
exaggerated in scale or in schematic in the interest of clarity and
conciseness.

[0025] FIG. 1 is a perspective view of a PDC element of the invention.

[0026]FIG. 2 is a perspective view of an earth boring drill bit having
the cutting elements of FIG. 1.

[0027]FIG. 3 is a partial cutaway perspective view of a PDC element
having two discontinuities with a `ring` configuration substantially
parallel to a top surface of the PDC element.

[0028] FIG. 4A is top view of a discontinuity having a `perforated`
configuration.

[0029]FIG. 4B is a perspective view of a discontinuity having a
`snowflake` configuration.

[0030]FIG. 4c is a perspective cutaway view of a PDC element having a
discontinuity with a `plate` configuration.

[0031]FIG. 5 is another is a partial cutaway perspective view of a PDC
element having two discontinuities with a `plate` configuration.

[0033]FIG. 7 is a top view of a discontinuity having a `ring`
configuration.

[0034]FIG. 8 is partial cutaway perspective view of a PDC element with
the discontinuity of FIG. 7 therein at an angle to a top surface of the
PDC element.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The description that follows includes exemplary apparatuses,
methods, techniques, and instruction sequences that embody techniques of
the inventive subject matter. However, it is understood that the
described embodiments may be practiced without these specific details.

[0036] The techniques described herein relate to a polycrystalline diamond
cutting (PDC) element configured to remain sharp during drilling. The PDC
element may be provided with discontinuities which are able to
selectively break off to continuously provide a sharp edge. Such features
may be used to enhance drilling operations by, for example, increasing
rates of penetration, reducing wear, enhancing drilling, etc. The cutting
efficiency of a PDC element for an earth boring drill bit may also be
influenced by the cutting edge preparation on the PDC elements.
Maintaining a sharp edge through the length of a run may be important to
improving the overall drilling efficiency of the drill bit.

[0037] Referring now to FIGS. 1 and 2, the PDC element 10 of the present
invention may be a preform cutting element for a fixed cutter rotary
drill bit 12 (as shown in FIG. 2). The bit body 14 of the drill bit 12
may be formed with a plurality of blades 16 extending generally outwardly
away from the central longitudinal axis of rotation 18 of the drill bit
12. Spaced apart side-by-side along a leading face 20 of each blade 16 is
a plurality of the PDC elements 10 of the invention.

[0038] Typically, the PDC element 10 has a body in the form of a
cylindrical tablet having a thin front facing diamond layer (or table)
22, and a substrate 24. The diamond table 22 may be bonded in a
high-pressure, high-temperature press to a substrate 24 of a less hard
material, such as cemented tungsten carbide or other metallic material.
The PDC element 10 may be preformed and then may be bonded onto a
generally cylindrical carrier 26, which may also be formed from cemented
tungsten carbide. Alternatively, PDC element 10 may be attached directly
to the blade(s) 16. The PDC element 10 has peripheral working surface 28
and end working surface 30 which, as illustrated, may be substantially
perpendicular to one another. The working surfaces 28 and 30 may also be
at other suitable angles.

[0039] The cylindrical carrier 26 may be received within a correspondingly
shaped socket or recess in the blade 16. The carrier 26 may be brazed,
shrink fit, press fit or otherwise secured into the socket. Where brazed,
the braze joint may extend over the carrier 26 and part of the substrate
24. In operation, the fixed cutter drill bit 12 is rotated and weight is
applied. This forces the PDC elements 10 into the earth being drilled,
effecting a cutting and/or drilling action.

[0040] Shown in FIGS. 3-8 are various PDC elements 10 that have
intentionally introduced regions of relative strength and weaknesses in
the general form of discontinuities 40a-d,a' which are formed about the
working surfaces 28, 30 of diamond table 22. The discontinuities 40a-d,a'
are geometrically oriented non-diamond structures embedded within or
formed upon the diamond table 22. These discontinuities 40a-d, a' may
form `fault plane weaknesses` as will be described further herein.

[0041] In operation, the cutting action of the PDC elements 10 may be
dependent upon the geometry of a cutting edge 50 along a periphery of
each of these PDC elements 10. The cutting edge 50 is continuously
renewed during operation by exposing and selectively failing along these
discontinuities 40a-d,a' within the PDC elements 10 to maintain a sharp
cutting edge 50.

[0042] The discontinuities 40a-d, a' within the PDC elements 10 may be
manufactured by providing within the diamond layer 22 of the preform PDC
element 10, a discontinuity 40a-d,a' with regular geometry, such as a
honeycomb pattern (as is shown in FIG. 4B), or a sieve or mesh pattern
(as shown in FIGS. 4A and 4C), or any one of numerous other patterns. The
discontinuities 40a-d, a' may also be perforated and/or stamped in a
separate operation or may be formed simultaneously with the PDC element
10. These discontinuities 40a-d,a' may preferably be made of a suitable
material such as tungsten carbide formed in a wire mesh, although
numerous other materials and geometrical configurations may also be
suitable. Other metallic materials for the discontinuities 40a-d, a' may
be suitable provided that they are compatible with the other materials in
the diamond table 22.

[0043] These discontinuities 40a-d, a' may produce areas of varying wear
resistance and impact strength in the finished PDC element 10 and,
therefore, provide for a self sharpening effect when in operation by
allowing select chipping or wearing of the element 10 along these
discontinuities 40a-d, a'. The open nature of the honeycomb pattern shown
in FIG. 4B or the mesh pattern in FIGS. 4A and 4C allow the diamond layer
to completely entomb the mesh pattern and thereby control how much
diamond material is `chipped away` under any particular set of drilling
conditions.

[0044] The preform PDC elements 10 with the introduced discontinuities
40a-d, a' may be made by sintering in a high temperature, high pressure
process together with the polycrystalline diamond grit and a tungsten
carbide substrate. Discontinuities that are formed along the cutting edge
50 within the diamond table 22 may react to operating loads to direct
shearing forces into the PDC element 10 to fracture the existing
polycrystalline diamond table 22 at the cutting edge 50 and to form a new
cutting edge from the existing cutting edge 50 as the PDC element 10 is
operated.

[0045] The discontinuities 40a-d, a' define `fault plane` weaknesses as
illustrated in FIGS. 3-8. In these figures the `fault plane` weaknesses
are aligned to be generally parallel to the top surface 30 of the cutting
element. In FIGS. 4B, 4C, 6, and 8, portions of the `fault plane`
weaknesses are not necessarily parallel to the top surface 30 of the
cutting element 10. The `fault plane` weaknesses may also be defined
(e.g., made and orientated) so that they will tend to fracture
simultaneously. However, it is also possible to have the stacked `fault
plane` weaknesses arranged such they are not aligned, as illustrated in,
for example, FIG. 4B.

[0046] Referring now to FIG. 3, the discontinuity 40a is depicted as a
mesh pattern 52 in the shape of a ring and defining areas of weaknesses
within the PDC element 10. FIG. 3 is a partial cutaway top view a cutting
element 10 showing two sets of discontinuities 40a defining a `fault
plane` weakness therein. The fault plane weakness runs substantially
parallel to a top surface 30 of the PDC element. Each sets of
discontinuities 40a is characterized as a segment of a `fault plane`
running within a diamond table 22 substantially parallel to the top
surface 30 and out to the cutting edge 50 of the PDC element 10. The mesh
pattern 52 is depicted as having a hole 55 therethrough. As shown,
multiple parts may be used to create multiple, stacked `fault plane`
weaknesses defined by the mesh pattern 52 as the PDC element 10 wears in
operation.

[0047] FIG. 4A is a top view of a discontinuity 40b formed as a particular
tungsten carbide mesh pattern 54 crack arrestor in a `perforated`
configuration. The mesh pattern 54 is interrupted by areas 64 without
mesh to allow diamond bonding around and through the mesh pattern 54
crack arrestor. These areas 64 without mesh may be formed around the
embedded discontinuities 40b as shown in FIG. 5. The mesh pattern 54 is
generally flat with a mesh periphery 57 which may be beveled or angled.
It is contemplated that the tungsten carbide mesh pattern 54 may be
extended to other geometries and sizes of PDC elements 10, as well.

[0048]FIG. 4B is a perspective view of a discontinuity 40c having
particular `snowflake` honeycomb pattern 72. The snowflake honeycomb
pattern 72 has a flat base 73 with a skirt 75 extending therefrom at an
angle. This flat base 73 of the discontinuity 40c has a flattened
honeycomb portion that covers only a portion of the cross-section of a
PDC element 10 (similar to the discontinuity 40d on cutting element 10 of
FIG. 4c). The flat base 73 has a ring shape with a skirt 75 extending
from portions of the flat base 73 to define the `snowflake`
configuration.

[0049]FIG. 4c is a perspective view of PDC element 10 having a
discontinuity 40d. The discontinuity 40d has a particular mesh pattern
54' similar to the mesh pattern 54 of FIG. 4A. As shown in this `plate`
configuration, the mesh pattern 54' is without holes 64. It will be clear
to those skilled in the art that FIG. 4c depicts the mesh pattern 54'
positioned on a portion of the diamond table 22 that is below (and
normally hidden by) the top surface 30 of the PDC element 10. The PDC
element 10 has been worn such that portions of the diamond layer 22 have
been removed along a fault plane weakness to reveal the mesh pattern 54'
as the new top surface 30 and angled side surface 25. Before wear and
removal of the diamond layer 22, the mesh pattern 54' may or may not
extend to the outer cylindrical surface of the PDC element, hence may or
may not be visible on its outer diameter until the diamond layer 22 is
chipped away.

[0050] Referring to FIGS. 5 and 6, A PDC element 10 with two `fault plane`
discontinuities 40b therein is depicted. FIG. 5 is a partial cutaway
perspective view of a PDC element 10 of FIG. 4c. The discontinuities 40b
run substantially parallel to the top surface 30 of the PDC element 10
with each mesh pattern 54 having a bevel 57 adjacent the cutting edge 50
curving away at an angle 58 as shown in FIG. 6. The discontinuity 40d (as
shown in FIG. 4c) may also be depicted by this same figure.

[0051] The induced `fault plane` discontinuities (e.g, 40b or 40d) may be
created by placing one or more of the layers of mesh pattern 54 within
the mold with the preformed PDC element 10 prior to a high-pressure,
high-temperature forming operation. The mesh pattern 54 may be tungsten
carbide, or other suitable compound, and after the forming operation, the
mesh may become integral with the PDC element 10. The `fault plane`
discontinuities 40a, 40d as illustrated in FIGS. 3 and 5 may not
necessarily need to be aligned to be parallel to the end working surface
30. The other discontinuities described herein may be formed in a similar
manner.

[0052]FIG. 6 shows a longitudinal cross-sectional view of the PDC element
10 of FIG. 5. This figure shows the two `fault plane` mesh pattern
discontinuities positioned in the diamond table 22. As shown in this
view, the bevels 57 of the discontinuities extending away from the top
surface 30 about the cutting edge 50 at an angle 58 as shown. This
configuration defines an angle of chamfer upon fault lines which, when
created, may be controlled by the angle 58 of the bevel 57.

[0053] The regular geometry of the discontinuities 40a-d, a' as described
herein may be generated in operation, allowing preferential wear by
creating non-planar fracture surfaces in the PDC element 10. For example,
as shown in FIGS. 5 and 6, the fracture surfaces may be defined along a
periphery of the discontinuity 40b at the angle 58 of the discontinuity
40b at relative strengths or weaknesses.

[0054]FIG. 7 shows a top view of the discontinuity 40a' of FIG. 3 having
a mesh pattern 52' in a ring configuration with a hole 55' therethrough.
The mesh pattern 52' is extended throughout an entire periphery (but not
in the center) of the discontinuity 40a'. The discontinuity 40a' may have
a mesh pattern 52' that is similar to the mesh pattern 52 of FIG. 4A. One
or more of the discontinuities 40a' or 40a may be positioned in a PDC
element 10 as shown, for example, in FIGS. 3 and 8. FIG. 8 is similar to
FIG. 3, but shows only one discontinuity 40a' therein, and is at an angle
to the top surface 30.

[0055] Many different types of mesh patterns may be extended to other
geometries and sizes of these parts, and is not limited to a solid mesh.
For example, the mesh patterns of the discontinuities herein may also be
formed into shapes such as a mesh pattern 52' (as shown in FIG. 7) or
other patterns. Additional shapes of the induced stress planes may be
specifically engineered as necessary for the desired performance.

[0056] The figures herein disclose a preform PDC element 10 suitable for
use in earth boring drill bits having a feature of regular geometry (such
as a honeycomb, or sieve) made with a tungsten carbide (or other
compatible material) embedded in the diamond table. The embedded
discontinuities 40a-d, a' may be introduced at strategic locations about
the cutting edge 50 of the PDC element 10 for use in earth boring drill
bits.

[0057] These embedded discontinuities 40a-d, a' may act to diffuse stress
concentration at the cusp of a forming crack and prevent or slow its
propagation. As a result, this may thereby limit damage to the diamond
table 22 due to overload or impact, and may also reduce the instances of
or at least minimize the effects of catastrophic failure. In essence, the
discontinuities 40a-d,a' may act as crack arrestors. The discontinuities
40a-d, a' may be sintered together with the polycrystalline diamond grit
and the tungsten carbide substrate under conditions of ultra high
temperatures and pressures, as is well known.

[0058] The PDC element configuration may be adjusted to optimize the
formation of new cutting edges during operation. The PDC element 10 may
be provided with higher abrasion resistance (i.e. more competent or hard)
to prevent the PDC element from wearing quickly and easily in service, or
dulling the cutting edge sooner than desired. Efforts to improve the
inherent abrasion resistance of the PDC element may revolve around
improved sintering (diamond to diamond bonding) and/or leaching the
catalyzing material out of the mesh pattern of the PDC element adjacent
to the working surfaces. The inherent abrasion resistance of the PDC
element may be increased by using finer diamond particles. The selected
diamond particles may be selected to avoid compromising other physical
properties, such as the impact resistance of the edge, with the diamond
crumbling away in service. While it may be desirable, from the abrasion
resistance and integrity of the PDC element point of view, to improve
sintering and diamond to diamond bonding, it may also be useful to ensure
that the edge is chipped or broken away in a controlled manner with as
small as possible chips when in operation.

[0059] As the figures also show, the discontinuities herein may reside
close to the cutting edge 50, and follow the edge geometry of the preform
PDC element 10, but they may also run along other surfaces. While in
operation, the discontinuity may not wear initially, but may be exposed
upon wear or impact damage of the surrounding areas during operation. An
exposed discontinuity 40a-d, a' may wear or chip away quickly to expose a
controlled geometry diamond cutting edge 50, allowing controlled the loss
of the diamond table 22 on subsequent impacts.

[0060] As shown, for example, in FIG. 6, the fault place weakness of the
PDC element 10 may be controlled by the bevel angle 58 of the peripheral
cutting edge working surface 28 set by the mesh pattern 54, and may be
adjusted with the addition of multiple mesh patterns 54.

[0061] The PDC element cutting 10 may be a polycrystalline diamond PDC
element 10 with a diamond table 22 integrally formed with a tungsten
carbide substrate. The diamond table 22 may be provided with one or more
discontinuities 40a-d, a' formed from non-diamond materials along the
cutting edge 50 that, as described above, continuously create and refresh
a fracture surface in the diamond table 22 while in operation by
continuously exposing a sharp cutting edge to the formation material
being cut. Suitable non-diamond materials for the discontinuities 40a-d,
a' may include a generally circular titanium `mesh` product and formed
with and without the center portion of the mesh pattern. In one example,
a non-diamond material for the discontinuity 40a may be a perforated
tungsten carbide mesh material formed in the geometrical shape of a disk.
Another preferred embodiment may be a mesh of discontinuities 40a made of
perforated tungsten carbide disc and formed into a `bellville washer`
like shape as shown in FIG. 4A but having a very large (over 70%) open
space, wherein the mesh 40a-d, a' is from about 55% to about 65%, and
preferably about 61% open.

[0062] The mesh geometry and material and processing may also be varied to
adjust for the thickness of the PDC element 10, (for disc or separation)
and the percentage of the open space. In addition, it may be possible to
reduce manufacturing time in sintering and, therefore, yield a sintered
product with an increased amount of cobalt now available from the
additional tungsten carbide available within the diamond table to make
these PDC elements 10.

[0063] Furthermore, there may be a residual stress reduction in the
finished PDC element 10 due to the layering associated with the mesh
40a-d, a' geometry. Additionally, this layering may not be in contact
with the formation initially, but may be exposed upon wear or impact
damage of the outer surface. It may wear or chip away quickly or slowly
as may be desired to expose a controlled geometry diamond cutting edge
50, thereby controlling the loss of the diamond table 22 from the
impacts.

[0064] Alternately the PDC element 10 of the present invention may
incorporate the use of scattered pellets or fibers of suitable materials,
such as aggregated carbon nano-rods 25 shown in FIG. 4c, (also known as
ACNR), that may not interfere with the quality of the final sintered
diamond product. These features may displace some of the diamond material
at the cutting edge 50, and because the discontinuity material is less
hard than the diamond material, it may `wear` into providing a cutting
edge similar to that as described above. In addition, the diamond grit
composition may be adjusted at the cutting edge 50 in order to allow for
a selective reduction in abrasion resistance (with an accompanying
increase in impact strength) adjacent to the cutting edge 50 to help
control the rate of chipping at the cutting edge.

[0065] The introduction of discontinuities 40a-d, a' along planes parallel
to the top surface 30 or angle 58 of chamfer (or alternately the edge
preparation angle) some distance into the diamond table 22 may allow the
cutting edge 50 of the diamond table 22 to flake off when worn to a
certain depth, thus exposing a fresh cutting edge 50 with an induced edge
geometry to contact the formation. This may be accomplished without
excessive loss of the diamond material.

[0066] While the present disclosure describes specific aspects of the
invention, numerous modifications and variations will become apparent to
those skilled in the art after studying the disclosure, including use of
equivalent functional and/or structural substitutes for elements
described herein. For example, one or more discontinuities of various
shapes may be implemented in one or more PDC elements 10. All such
similar variations apparent to those skilled in the art are deemed to be
within the scope of the invention as defined by the appended claims.

[0067] Plural instances may be provided for components, operations, or
structures described herein as a single instance. In general, structures
and functionality presented as separate components in the exemplary
configurations may be implemented as a combined structure or component.
Similarly, structures and functionality presented as a single component
may be implemented as separate components. These and other variations,
modifications, additions, and improvements may fall within the scope of
the inventive subject matter.

[0068] Whereas the present invention has been described in particular
relation to the drawings attached hereto, it should be understood that
other and further modifications apart from those shown or suggested
herein, may be made within the scope and spirit of the present invention.